The main aim of this work was to investigate the nature, distribution and transmissibility of tetracycline resistance (Tc<sup>R</sup>) genes among ruminant anaerobic bacteria. Two Tc<sup>R</sup> rumen strains of <I>Butyrivibrio fibrisolvens,</I> 1.230 and 1.23, were able to transfer the resistance phenotype to the type strain, 2221<sup>R</sup> although a third Tc<sup>R</sup> strain, 1.210, could not. PCR amplification of 16S rDNA sequences showed that the three isolates were phylogenetically distinct from the recipient strain, but related to each other. Hybridisation work suggested the presence of two chromosomal Tc<sup>R</sup> determinants among the <I>B. fibrisolvens </I>isolates. All three strains contained a non-transferable <I>tet</I>(O) gene, 100% identical at the nucleotide level with <I>tet</I>(O) from <I>S. pneumoniae. </I>The mobile Tc<sup>R</sup> determinant present in strains 1.230 and 1.23, proved to be a novel ribosome protection <I>tet </I>gene, <I>tet</I>(V), whose gene product shares only 68% amino acid identity with its closest relatives, TetO/TetM and has G+C content considerably higher than that of other <I>B. fibrisolvens </I>genes. <I>tet</I>(V) was also identified in two Australian rumen <I>B. fibrisolvens </I>strains, in the rumen anaerobes <I>Selenomonas ruminantium </I>and <I>Mitsuokella multiacidus, </I>and in a pig isolate of <I>M. multiacidus. </I>These results provide evidence for gene transfer between obligate and facultative anaerobes from different gut ecosystems and different geographical locations. PFGE demonstrated that mobile chromosomal elements 40-50 kb in size, Tn<I>B1230 </I>and Tn<I>B123, </I>with preferred insertion sites in the recipient genome mediated the transfer of <I>tet</I>(V) in <I>B. fibrisolvens. </I>No homology was found between Tn<I>B1230</I> and regions from Tn<I>916</I> and Tn<I>5253. </I>Tn<I>B1230</I> is not associated with <I>tet</I>(V) in the other bacterial strains, suggesting that a diverse range of elements carry the gene in different bacteria. Although <I>tet</I>(V) is chromosomally encoded in the majority of the strains examined, there is some evidence that the gene may be located in a plasmid in <I>S. ruminantium </I>FB32 and FB34.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:286850 |
| Date | January 1998 |
| Creators | Barbosa, Teresa Maria Leite Martins |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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